Re: [gccsdk] exec() possibly a problem

In message <20150206110347.61052205A0@orac.inputplus.co.uk> you wrote:

> Hi Ron,
>
> > My useage here is in fact wrong, it appears that command and args are
> > wrapped in single quotes for a subshell. (Also done in a shellscript)
>
> No, that's too simplistic. Unix shells like dash follow
> http://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html
> in their processing of the backslash escape, and single and double
> quotes.
>
> > $ $PATH/sh -c 'printf "hello...\\n"'
> > hello...
> > $
> > all good
> > Simplifies things, now just the \\n being needed across the new
> > process.
>
> I've only skimmed this thread to date, but be aware that there are three
> processes parsing that command above. The dash shell that's printed the
> `$ ' prompt. The sh you explicitly start. And the printf that's either
> a built-in to the shell or a separate executable that's processing the
> argv[] its main has been passed. All three of them are happy to
> interpret a backslash-escape in some circumstances.
>
> As an example, double quotes, which allow more interpolating, aren't
> necessary above. Another layer of single quotes can be used, with them
> mechanically being escaped, e.g.
>
> $ sh -c 'printf '\''hello...\n'\'
> hello...
> $
>
> Cheers, Ralph.

Thanks for the email, Ralph. Unfortunately there is still a differance
between RISC OS dash and (on) Linux dash.

The exanple above gives an error on RISC OS, haven't checked it on Linux
yet, I assume you have.

$ $PATH/sh -c 'printf '\''hello...\n'\'
hello...n$

still not acting on the \n
Beware people with an outline font, those are all single quotes.

Ron M.



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